Hello Sebastian: The figure that you shared is interesting. Here are three observations/ things to check: 1. Is the integration time per point the same during the in-situ measurements? I think that it is otherwise the raw data would not be on the same scale as the other scans. 2. The raw data shows about the same edge step so I believe you are correct and the signal is the same in all the measurements, so somehow during the in-situ part additional noise was picked up. Was the in-situ apparatus causing some vibrations or noise in the measurement? Kind regards, Shelly From: Ifeffit On Behalf Of Sebastian Kunze Sent: Monday, April 29, 2024 7:17 AM To: ifeffit@millenia.cars.aps.anl.gov Subject: [Ifeffit] Origin of noise in Ag K-Edge Greetings, I recently did in-situ QEXAFS at Ag K-edge, expecting to see structure loss starting from crystalline (metallic) state. While we can see that, in addition we also see an increase in noise(?) in the xanes region (compare start and ZjQcmQRYFpfptBannerStart This Message Is From an External Sender This message came from outside your organization. ZjQcmQRYFpfptBannerEnd Greetings, I recently did in-situ QEXAFS at Ag K-edge, expecting to see structure loss starting from crystalline (metallic) state. While we can see that, in addition we also see an increase in noise(?) in the xanes region (compare start and end in the attached image). I am confused by this because the amount of material did not change, so I did not expect a difference in the signal/noise ratio at the absorption edge. And it is reproducible across several samples, so not instrument related. Could anyone point me in the right direction as to what I am missing? Thank you! Best, Sebastian Kunze

Sebastian, What is happening “in situ”? Are you heating the sample, flowing gas, or changing some other external conditions? The cleaner spectra are also those with larger oscillations, implying a more uniform local environment. That might suggest that the less clean spectra are from samples with more pinholes or non-uniformity in the bulk distribution of sample particles within the beam. --Matt From: Ifeffit on behalf of Sebastian Kunze Date: Monday, April 29, 2024 at 8:21 AM To: ifeffit@millenia.cars.aps.anl.gov Subject: [Ifeffit] Origin of noise in Ag K-Edge Greetings, I recently did in-situ QEXAFS at Ag K-edge, expecting to see structure loss starting from crystalline (metallic) state. While we can see that, in addition we also see an increase in noise(?) in the xanes region (compare start and ZjQcmQRYFpfptBannerStart This Message Is From an External Sender This message came from outside your organization. ZjQcmQRYFpfptBannerEnd Greetings, I recently did in-situ QEXAFS at Ag K-edge, expecting to see structure loss starting from crystalline (metallic) state. While we can see that, in addition we also see an increase in noise(?) in the xanes region (compare start and end in the attached image). I am confused by this because the amount of material did not change, so I did not expect a difference in the signal/noise ratio at the absorption edge. And it is reproducible across several samples, so not instrument related. Could anyone point me in the right direction as to what I am missing? Thank you! Best, Sebastian Kunze